I've tried lots of stuff - but even though the dyes I use now are more expensive it doesn't take a lot to do them.
The hen mallard will dye up really nice, but you REALLY need to clean the feathers!
On some colors I'll leave the fuzz on the bottom and others I don't. I usually trim the fluff off the bottom of the feather and cut the bottom of the stem. Take the feathers and get a water tight container, I use plastic Maxwell house cans and use a couple of tablespoons of borax and Dawn dishwashing liquid. Don't over fill with water you have to be able to shake them. I shake them up then let them sit for 15-20 mins then shake again let sit again. It might seem a long time but when you go to dye you want those feathers soaking wet
Use a strainer and drain and rinse the feathers really well. GET YOUR OWN STUFF FOR DYEING!!!!
If you're not going to dye them right away, after you rinse squeeze them between paper towels and toss them in an old pillow case and make sure to put an anti-static sheet in with them and dry them with heat for 5 minutes then just air. When they're dry put them in zip lock bags.
This will get you started. If you need any more help with the dyeing just let me know and I'll help you out as much as I can.